STUDIES ON MICROSTRUCTURAL CHANGES of PARBOILED and PUFFED RICE

Abstract

Parboiled rice as well as puffed rice kernels were examined using Scanning electron microscopy for studying the ultra-structural changes that take place during the processes involved. the transverse sections of polished parboiled rice grains revealed an approximately 0.1 mm thick peripheral endosperm layer. In this layer the starch granules appeared swollen and embedded in a protein matrix, while those in the inner endosperm were transformed into a fused mass of gelatinized starch. Transverse sections of puffed rice kernels revealed the various stages of gelatinized starch cells expansion due to high pressure steam formed inside the rice kernel during the high temperature short time treatment for puffing. the resulting cellular expansion, creating many void spaces and air vacuoles, imparted a highly porous and expanded structure to the puffed rice kernel. the peripheral thin layer formed during parboiling of rice expanded and enveloped the puffed rice kernel and prevented it from bursting.